He, being dumb, did not use antifreeze, only straight water, last time he filled his cooling system. Portland experienced an uncharacteristic freeze this winter, and guess what? Water freezes....

Long story short, he has a cracked engine block in his 1990 325is automatic.

In my garage, I happen to have the powertrain from my old 1987 325es. Yes, it would suck to swap a b27 in place of a b25, but at this point he doesn't really care about power and just wants a car that goes. Would it be possible to just drop the b27 in? What modifications would be necessary? 'es ECU?

He, being dumb, did not use antifreeze, only straight water, last time he filled his cooling system. Portland experienced an uncharacteristic freeze this winter, and guess what? Water freezes....

Long story short, he has a cracked engine block in his 1990 325is automatic.

In my garage, I happen to have the powertrain from my old 1987 325es. Yes, it would suck to swap a b27 in place of a b25, but at this point he doesn't really care about power and just wants a car that goes. Would it be possible to just drop the b27 in? What modifications would be necessary? 'es ECU?

You'll have to drill holes in his tranny bell housing for the flywheel sensors and drill a hole in the flywheel for the pick up stud. You'll also need the harness to handle the sensor wiring or at least kludge them into the ECU.

Quotedaniel
you could either do that or find an M20B25 for pretty cheap. or theres always the M50...

You missed the whole point of the post...his brother has the M20B25 and he needsa to know if the M20B27 will swap in without too much trouble. The M20B27 is available and sitting in Evan's garage(or wherever) and it will cost nothing. The M50/52 swap will involve money and third party stuff

Quotedaniel
you could either do that or find an M20B25 for pretty cheap. or theres always the M50...

You missed the whole point of the post...his brother has the M20B25 and he needsa to know if the M20B27 will swap in without too much trouble. The M20B27 is available and sitting in Evan's garage(or wherever) and it will cost nothing. The M50/52 swap will involve money and third party stuff

I understand that. I suggested the used M20B25 because then one wouldnt have to worry about changing out the electrics and parts of the drivetrain, which you mentioned would be necessary with the B27 swap. So with that said, I then drifted off into M50 land since that also requires electric work and a few other modifications.

IMO if you are going to do a swap, get a good block and rebuild the motor. Putting in an E motor is not worth the effort even if it is free. You still might have to replace seals and injectors etc if the lump has been sitting unused very long. Also resale value would suffer if you put that motor in it. Just tell your bro that this is called stupid tax and hopefully he learns that $10 for antifreeze is well worth the cost!